Crimes at Sea Act 1979

Key rules include:

• Australian ships on interstate or international voyages: The criminal laws of whichever State or Territory the ship is "connected with" (usually where it's registered, licensed, or based) apply to any acts committed on board.
• Foreign ships heading to Australia: If a crime occurs on a foreign ship on its way to an Australian port, the criminal laws of the State or Territory where the accused eventually lands apply — but the Attorney-General must give written consent before most prosecutions can proceed.
• Australian citizens on foreign ships: If an Australian citizen (who is not a crew member) commits an act on a foreign ship beyond Australian waters, the laws of their home State or Territory apply.
• Offshore oil and gas areas: Criminal laws of the adjacent State or Territory apply to activities connected with exploring or exploiting the continental shelf (e.g., oil rigs).
• Timor Gap Zone: Special provisions apply to the joint petroleum exploration zone that Australia formerly shared with Indonesia (and later East Timor), extending Northern Territory criminal law to that area.

Special safeguards and procedural rules

• Jury trials are required for serious (indictable) offences tried under this Act.
• Prosecution of foreign nationals requires the Attorney-General's sign-off, and if another country has jurisdiction over the ship, that country's government must also consent — unless the act is piracy.
• A person already dealt with under East Timor law for the same act cannot be prosecuted again under this Act (protection against double punishment).
• Judges can pause (stay) proceedings if parallel prosecutions are happening elsewhere, to prevent unfairness.
• Existing Commonwealth laws (like parts of the Crimes Act 1914) are carefully switched off where State/Territory law is being applied instead, to avoid overlap and confusion.
• Arrangements can be made between the Commonwealth and State/Territory governments to allow State/Territory authorities (like police) to exercise powers under the applied laws.

Why does it matter?

Without this Act, there would be a legal black hole — crimes committed beyond Australia's coastal waters could go unprosecuted simply because no law clearly applied. This Act ensures that Australian criminal law reaches ships at sea and offshore installations, while respecting international law (such as requiring consent from foreign governments before prosecuting acts on their ships).